Arsenic poisoning in drinking water is identified as one of earth's worst natural disaster. For example, in Bangladesh, an estimated 77-95 million people are drinking groundwater containing at least about 50 μg/L (or about 0.05 mg/L) maximum contamination level (MCL) from 10 million tubewells. Prolonged drinking of such contaminated water has caused serious illnesses. These illnesses include hyperkeratosis on palms and/or feet, fatigue symptoms of arsenicosis, cancer of the bladder, skin and other organs, etc.
In groundwater, with a pH between approximately 6.5 to approximately 7.5, arsenic may be present in two oxidation states, namely, As(III) in H3AsO3 and As(V) in H2AsO4− and HAsO42−. It is well known in the art that about 50% or more of total arsenic is present as the neutral H3AsO3 at groundwater pH. The remaining percentage (up to about 50%) is generally divided equally in two As(V) species: H2AsO4− and HAsO42−. To remove all three species without chemical pretreatment, regeneration and/or production of toxic wastes, an ideal filter is needed.
While efforts to resolve this problem have been underway for a decade, there is no readily available implementable solution on a widespread scale—both individual homes and the community. Consequently, to resolve this crisis, society needs a way to remove as much arsenic as possible from water. The ideal system should remove arsenic without degrading other water characteristics, such as taste and odor. It may also be beneficial if other minerals and elements in the water can be removed. It would also help if the ideal system is user-friendly, easy to maintain (including removal and safe disposal of contaminated residues), and sustainable over many years.